The field of this invention is that of metal-oxide-semiconductor (MOS) integrated circuits and the invention relates more particularly to an MOS integrated circuit having a large number of terminal pins or the like arranged in an array around an array of shift registers or the like and having a novel metal programmable matrix arranged for accommodating interconnection of any of the outputs of the shift registers with any of the terminal pins in an advantageously compact and economical manner.
Where known MOS integrated circuits have had MOS circuit elements forming components such as shift registers or the like and have had a large number of the shift registers arranged in an array to be connected with a large number of terminal pins or the like such as the input pins of an output buffer, the integrated circuit structure has typically provided metal conductor means connecting the respective register outputs and the output buffer input pins to a gate programmable logic array and has then programmed the logic array as necessary to provide the desired interconnection of the register outputs with the buffer input pins. In that arrangement, the basic integrated circuit structure has been programmable for achieving desired versatility but the amount of interconnecting metal conductor means required in the structure has made the circuit bar or chip size relatively large, the programming has been required at the gate level of the integrated circuit structure, and the system has required provision of extra MOS elements embodied in the logic array. In other known MOS integrated circuits, data buss lines for the respective registers have been run around the registers. Conductors from the register outputs and from the inputs to the output buffer pins or the like have then been run under each of the busses. Each of those conductors has been provided with potential contact areas formed by thin oxide coatings at a proposed juncture with each data buss and the system has then been programmed in a multistep process requiring opening of selected thin oxide coatings to provide a selected programmed contact pattern followed by provision of the metal data buss means to connect to the contact pattern to complete the programming. Again the programming procedure is unduly slow and there is risk of a yield problem such as may be caused by the occurrence of too thin oxide coatings at the potential contact areas which are not actually used in forming contact openings.